Jol was invented around 1968 on a system using punch cards and no TSO and years before REXX. The computer had less than a megabyte and so Jol had to run in a 20K partition which was shared with the IBM Reader program. There were no interactive facilities available then, and tapes were used for main storage, and disks were tiny.
Since then, to say many things have changed in the IBM Mainframe world is a vast understatement!
Over the years, many facilities were added to Jol to incorporate new advances in technology.
NOTE: A detailed list of Jol instructions may be found at www.JolUCL.com/JolDoc